Release of Copper, Chromium and Arsenic from CCA-C Treated Lumber in Estuaries

Laboratory and field studies were conducted to determine the rates of release for Cu, Cr and As from CCA-C treated southern yellow pine in estuaries. Retention of the CCA-C preservative was shown to vary across the surface of the wood (4•5–64 kg m−3), however, the ratio of the elements present as oxides was close to the specified preservative treatment levels throughout the wood. Results of the leaching studies showed that the release of Cu, Cr and As was continuous throughout the 90 day leaching period and, in general, the leaching was highest for Cu and lowest for Cr. Initial 12 h fluxes for these elements ranged from 9 to 28×10−10 mol mm−2 day−1for Cu, 0•4 to 1•9×10−10 mol mm−2 day−1for Cr, and 0•2 to 5•2×10−10 mol mm−2 day−1for As. The rate of release for these elements decreased between 0•5 and 2 orders of magnitude following 90 days leaching. Long-term (90 day) Cu and Cr leaching rates were highest in wood where CCA-C retention levels were >35 kg m−3. In contrast, long-term As leaching rates increased in wood where CCA-C retention levels were <35 kg m−3. Differences in the As:Cr and Cu:Cr ratios were measured in CCA-C treated lumber samples removed from a bulkhead following 14 years weathering. The greatest changes in the elemental ratios were measured in wood submerged in the subtidal zone where a 52% decrease in the As:Cr and Cu:Cr ratios were measured.